In an application such as an airbag squib driver, the firing currents are regulated to avoid any inadvertent firing. FIG. 1 shows a conventional deploy circuit 100 which generally comprises gate drivers 102 and 104, High Side Driver (HSD) Q1, a current limiting Low Side Driver (LSD) Q2, and pins or terminals 104, 106, 108, and 110. Both of the HSD Q1 and LSD Q2 are capable of driving a firing current of 1-2 A to inflate an airbag (through squib 112 and capacitors C1 and C2) and are is typically a high voltage LDMOS transistors (preferably N-type MOS transistors). The firing currents are generally regulated in order to help ensure a well controlled firing event, but conventional deploy circuits 100 have undesirable accuracy of current regulation and/or have an unavoidable systematic offset between two matched LDMOS transistors.
Some examples of conventional circuit are: German Patent Appl. No. 102004049082; and Baker et al., “CMOS Circuit Design, Layout, and Simulation,” IEEE Press, 1998, pp. 136-139.